1. Field of the Invention
This invention concerns corrosion inhibitor combinations, and antifreeze and heat transfer compositions containing such combinations. More particularly, this invention concerns solutions containing potassium, with aliphatic monocarboxylate, hydrocarbyl dicarboxylate, hydrocarbyl triazole, with one or more silicate, phosphate, borate, or nitrate used in corrosion inhibitor compositions and processes.
2. Description of Related Information
Metallic materials used in heat-transfer systems, such as internal combustion engines, undergo corrosive attack from heat transfer fluids, such as aqueous media containing antifreeze. The resulting metal damage, such as pitting and cavitation, causes perforations or other defects which can lead to fluid loss and system failure. Also, corrosion products tend to form insoluble salts which may block coolant passages or reduce heat transfer.
Various corrosion inhibitors have been added to heat transfer fluids to reduce corrosion of metallic systems. U.S. Pat. No. 4,647,392 (Darden et al.) discloses corrosion inhibitors using aliphatic monobasic acids or salts, hydrocarbyl dibasic acids or salts and hydrocarbyl triazole. U.S. Pat. No. 4,657,689 (Darden) discloses corrosion inhibitors containing aliphatic monobasic acids or salts, hydrocarbyl dibasic acids or salts, hydrocarbyl azoles and specific hydrocarbyl alkali metal sulfonates. These carboxylate-containing materials provide excellent corrosion inhibition properties.
Frequently, various corrosion inhibiting formulations or concentrates, such as antifreezes, are combined during use. Typically, antifreeze formulations are added to heat transfer fluids, such as in motor vehicle engine cooling systems, to prepare for winter temperatures and as fluid loss replacement. Commercial antifreeze formulations contain various inhibitor technologies. If two or more antifreezes containing different types of inhibitors are used in one cooling system, a composition having mixtures of the antifreeze formulations is generated.
The effectiveness of mixtures of different corrosion inhibiting formulations will at least in part depend on the compatibility between the components of each formulation. For example, the combination of certain carboxylate-containing corrosion inhibiting compositions with other corrosion inhibiting compositions having silicates, phosphates, borates, nitrates and/or other components, can have limited compatibility. This limited compatibility can result in precipitation of some of the corrosion inhibiting material and/or result in a reduction in corrosion inhibiting properties.
Corrosion inhibiting combinations are therefore needed which are effective in inhibiting corrosion using carboxylate-containing compositions in combination with other materials useful in corrosion inhibiting compositions which combinations are compatible and at least maintain corrosion inhibiting properties.